With MSR_AMD64_SEV_DEBUG_SWAP enabled, the guest is not expected to
receive a #VC for reads or writes of DR7.
Update the SNP_FEATURES_PRESENT mask with MSR_AMD64_SNP_DEBUG_SWAP so
an SNP guest doesn't gracefully terminate during SNP feature negotiation
if MSR_AMD64_SEV_DEBUG_SWAP is enabled.
Since a guest is not expected to receive a #VC on DR7 accesses when
MSR_AMD64_SEV_DEBUG_SWAP is enabled, return an error from the #VC
handler in this situation.
Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxx>
Reviewed-by: Carlos Bilbao <carlos.bilbao@xxxxxxx>
Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Reviewed-by: Pankaj Gupta <pankaj.gupta@xxxxxxx>
---
Changes:
v4:
* rebased on top of SNP feature negotiation
v2:
* use new bit definition
---
arch/x86/boot/compressed/sev.c | 2 +-
arch/x86/kernel/sev.c | 6 ++++++
2 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 014b89c89088..f6123808be42 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -313,7 +313,7 @@ static void enforce_vmpl0(void)
* by the guest kernel. As and when a new feature is implemented in the
* guest kernel, a corresponding bit should be added to the mask.
*/
-#define SNP_FEATURES_PRESENT (0)
+#define SNP_FEATURES_PRESENT MSR_AMD64_SNP_DEBUG_SWAP
void snp_check_features(void)
{
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index b031244d6d2d..a515eb880970 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -1620,6 +1620,9 @@ static enum es_result vc_handle_dr7_write(struct ghcb *ghcb,
long val, *reg = vc_insn_get_rm(ctxt);
enum es_result ret;
+ if (sev_status & MSR_AMD64_SNP_DEBUG_SWAP)
+ return ES_VMM_ERROR;
+
if (!reg)
return ES_DECODE_FAILED;
@@ -1657,6 +1660,9 @@ static enum es_result vc_handle_dr7_read(struct ghcb *ghcb,
struct sev_es_runtime_data *data = this_cpu_read(runtime_data);
long *reg = vc_insn_get_rm(ctxt);
+ if (sev_status & MSR_AMD64_SNP_DEBUG_SWAP)
+ return ES_VMM_ERROR;
+
if (!reg)
return ES_DECODE_FAILED;
--
2.39.1
